An estimated 6,000 to 17,000 students in Montgomery County's public secondary schools and 500 to 700 students in Prince George's County have not been immunized against measles as required by a recent Maryland regulation.

Any public school student not complying with the regulation, which applies to all students in Maryland public and private secondary schools, by the statewide deadline of Dec. 1 will be sent home from school that day, according to school spokesmen in both counties.

The sluggish response to the regulation, which was publicized last June in Montgomery County and this fall in Prince George's County, has prompted school officials to initiate what they say have been time-consuming record searches and letter-writing and phone-calling campaigns to parents of noncomplying children. "This is a medical and parental responsibility which the schools have had thrust upon them," said William Hauptman, Health Coordinator for Montgomery County schools.

Earlier this fall, both counties sent letters and forms to parents of secondary school youngsters whose records showed histories of uncertain or no immunization. In addition, Prince George's County principals were instructed to meet personally with non-complying students, according to spokesman John Aubuchon. In Montgomery County, principals were told in October to send letters to noncomplying students and to contact them before Thanksgiving. Ten to 30 percent of Montgomery County's 58,000 secondary public school students have not complied with the regulation.

This is the first immunization requirement in Maryland for secondary school students in grades seven through 12. According to Hauptman, epidemics of measles, which he said can have serious and permanent side effects such as poor vision and brain damage, have occurred in secondary school populations around the country. Hauptman said there have been small outbreaks of measles in Montgomery County in the last few years. In Prince George's County last year, there were six cases of measles at Bowie Senior High, according to Sally Bucklee, spokeswoman for the Prince George's Health Department.

Children in kindergarten through sixth grade are required to be immunized against polio, measles, rubella, diptheria, pertussis (whooping cough), and tetanus.

Parents Montgomery County public school children can comply with the measles immunization requirement by having their youngsters return forms to the school filled out with one of five items: A pysicians signature attesting to the child's vaccination and the date; a physician's statement saying there is a medical reason why the youngster should not have a vaccination; a parental statement that says the youngster has been immunized, but the records have been lost; a note of religious exemption, or a physician's or parent's statement saying the youngster has had measles.

In Prince George'c County, public school secondary students have a similar form which should be filled out and returned to the school. Prince George's students can also indicate that the youngster is sheduled for an appointment with a physician to have the vaccine or a blood test to determine immunity.

Maryland requires that children, at age one or older, have the live measles vaccine, according to state health department spokesman John McAvinue. The killed meassles vacine has not been available since 1967 nor used extensively since 1966 in Maryland. Montgomery and Prince George's sent letters to the parents of any youngster whose immunity record left any doubt that the child met the state requirement. however, neither county requires cerfication of the type of measles vaccine.

Dr. Eugene Rosenberger, chief of epidemiology for the Montgomery County Health Department, said any child who has been or may have been vaccinated with the killed vaccine should be revaccinated with live vaccine.

"The safest way to be sure of immunity is a measles titer," said Dr. Mary Alice Fox, chief of Infant and Child Services for Montgomery County. Physicians can give a blood test to determine a youngster's titer - the level of antibodies in the blood which, when high enough, keeps the child protected against measles. However, Hauptman said that getting the lab results can take a week to 10 days.

To aid students who need measles vaccinations, the Prince George's Health Departmnnt helf one-day clinics in each of the county's 61 public secondary schools in November. Bucklee said the health department estimates that several thousand students were vaccinated at the clinics.

Both Montgomery and Prince George's counties will sponsor clinics for immunizations Wed., Nov. 30. In Montgomery County, the clinic will be from 3 to 9 p.m. at Walter Johnson High School at 6400 Rock Spring Drive in Bethesda. In Prince George's County, the clinic will be from 6 to 8 p.m. at the Health Department on Hospital Road in Cheverly.

The Montgomery County Health Department will have extended hours at its walk-in himmunization health clinics:

Monday, Nov. 28 2-8 p.m. - Rockville Health Clinic, 50 Monroe St., Rockville 279-1645, and Northeast Health Center, 3460 Laytonsville Rd., Olney, 774-0880.

Monday, Nov. 28 4-8 p.m. - Piney Branch Middle School, 7510 Maple Ave., Takoma Park, 270-6400.

Monday, Nov. 28 5-8 p.m.: Central Clinic, 12701 Twinbrook Pkwy., Rockville.

Tuesday, Nov. 29 2-8 p.m.: Rocking Hoese Health Center, 4701 Randolph Rd., Rockville, 881-9240; Bethesda Health Center, 4848 Cordell Ave., Bethesda, 654-5525; Gaithersburgh Health Center, 542 N. Frederick Ave., Gaithersburgh, 926-6000.